The patent and journal literature is replete with information concerning "liposomes" which term, as used herein, will mean bilayer vesicles derived from amphiphilic molecules which are either anionic or nonionic in charge. The liposomes can be unilamellar or multilamellar. Thus, "liposomes" can include vesicles derived from natural phospholipids as well as those from synthetic nonionic amphiphilic compounds which are sometimes called "niosomes".
The cosmetic use of such materials is rapidly gaining importance in the cosmetic marketplace. Recent summaries of information concerning liposomes include two articles in the May, 1990 issue of Cosmetics & Toiletries, Vol. 105: "The Application of Liposomes to Cosmetics" by Suzuki et al. on page 65ff and "Liposomes in Dermatological Preparations Part I" by Lautenschlager on page 89ff, an article in the July, 1990 issue of Cosmetics & Toiletries: "Liposomes In Dermatological Preparations Part II" by Lautenschlager on page 63ff ("Lautenschlager II"), as well as in the June, 1990 issue of Soap/Cosmetics/Chemical Specialties: "Liposomal Cosmetics" by Wendel et al. on page 32ff, the 1979 issue of International Journal of Cosmetic Science, Vol. 1: "Dispersions of lamellar phases of non-ionic lipids in cosmetic products" by Handajani-Vila et al. on page 303ff, and the January/February, 1989 issue of Journal of the Society of Cosmetic Chemists, vol. 40: "Liposomes: From theoretical model to cosmetic tool" by Strauss. The Strauss article notes that liposomes can encapsulate water-soluble cosmetics in their aqueous compartments. It states that detergents and surfactants are added, but are later removed by dialysis or gel filtration to form the liposomes (FIG. 2) while page 56 states that surfactants can be encapsulated in liposomes. Other examples of liposome preparation are found in U.S. Pat. Nos. 4,438,052 to Weder et al., 4,536,324 to Fujiwara et al. (nonionic liposomes), 4,708,861 to Popescu et al., 4,853,228 to Wallach et al. (nonionic liposomes--charged surfactants can be added to alter the ionic nature of the liposome formed), and 4,911,928 to Wallach et al. and the Bulletin of the Chemical Society of Japan, "Synthetic Bilayer Membranes with Anionic Head Groups", Kunitake et al., Vol. 51, No. 6, page 1877ff, 1978 (liposomes from synthetic anionic surfactants).
For cosmetic uses, liposome-containing formulations are generally in the form of lotions or creams which provide a vehicle which retains the bilayer structure of the liposomes. Liposomes, particularly those derived from phospholipids such as lecithin, are sensitive to other compounds which can lyse the bilayer forming the liposome particles. Lysis eliminates the presence of the vesicles comprising the liposomes and any cosmetic material such as a humectant carried within the aqueous interior compartment of the liposome is released into the surrounding aqueous media.
Skin creams and lotions are generally left on the skin or hair and are not rinsed off. It would be of significant cosmetic importance if liposomes could be included in products such as shower gels and hair shampoos. These products would both cleanse the body and impart the beneficial properties of liposomes to the skin and hair even though a shower gel or hair shampoo is normally rinsed away. Although the literature is somewhat contradictory on this point, anionic surfactants of the type typically used in shower gels and shampoos such as sodium laureth-2 sulfate act to lyse liposome vesicles. The liposomes are not stable in the presence of such surfactants and any beneficial effect they might have is reduced or eliminated by such lysis.
Liposome stability is particularly important when the liposomes are used to deliver an active ingredient such as a moisturizer or vitamin. For example, page 36 of the Wendel et al. article, supra, states "liposomal liquid soaps or shampoos generally cannot be formulated" in referring to natural phospholipid-derived liposomes. Wendel et al. further teach that liposomes are "quite stable in products with amphiphilic surfactants such as ethanol or ethylene glycol". U.S. Pat. No. 4,752,572 to Sundberg et al. teaches that liposomes are lysed by the addition of a surfactant with a critical micelle concentration of at least 0.1 millimole and states that examples of anionic surfactants used to lyse liposomes are sodium cholate and sodium dodecyl sulfate. Page 66 of the Lautenschlager II article states ". . . it is impossible to formulate liposomal liquid soaps or shampoos . . ." while page 70 refers to a stable oil-in-water cream containing liposomes as well as 0.5% polysorbate and 0.5% sorbitan mono-oleate as an example of a stable liposomal cream with very low proportions of emulsifiers.
U.S. Pat. No. 3,957,971 to Oleniacz teaches liposome suspensions containing entrapped humectants where the liposomes comprise a ternary mixture of lecithin, dicetyl phosphate and cholesterol and the humectant can be sodium pyroglutamate or glutamic acid. Contrary to other journal reports, Oleniacz teaches that such liposomes can be delivered from a vehicle containing anionic or amphoteric surfactants. Example 15 gives a shampoo formulation containing an anionic surfactant--triethanolammonium lauryl sulfate, ethanol, another surfactant--bis(2-hydroxyethyl)alkylamine oxide, ethanol and an aqueous composition containing liposomes in which sodium pyroglutamate was entrapped. The instructions state that the four ingredients are merely mixed together at room temperature while maintaining a pH of 5-6 until the solid components dissolve. Unlike Example 13 of Oleniacz where the stability of humectant-containing liposomes in the presence of 0.1 weight volume percent of various surfactants is reported, there is no indication that stable liposomes were present in the resulting shampoo composition. No specific order for mixing the ingredients together is given for Example 15.
In their article in Physica B 156 & 157 entitled "Neutron Small Angle Scattering of Liposomes in the Presence of Detergents" on page 477ff, Nawroth et al. conclude that small amounts of detergents such as bile salts (taurodexycholate sodium salt) can be incorporated into lecithin-based liposomes without destroying their structure. The liposomes were stabilized by the charged detergent. Nonionic detergents did not help to stabilize the liposomes while anionic and cationic detergents did. In this work, the detergents were incorporated into the liposomes during their formation.
Unlike the liposomes which are the subject of this invention, U.S. Pat. No. 4,885,159 to Miyake et al. teach a hair cosmetic which is a polymer vesicle obtained from the polymerization of a surfactant monomer vesicle having a quaternary ammonium cation and a polymerizable anion as a counterion. The products are said to be useful as a hair rinse to condition the hair. In addition to the polymeric vesicles, anionic surfactants can also be present.